[upl-image-preview uuid=2dd08e71-5b29-443b-8462-ed3cb82fecee url=https://storage.hamcq.cn/2025-08-27/1756274025-485157-2dd08e71-5b29-443b-8462-ed3cb82fecee.png alt={TEXT?}] [upl-image-preview uuid=a486b31d-2c58-4698-b5d3-8fd74e96f855 url=https://storage.hamcq.cn/2025-08-27/1756274025-615038-a486b31d-2c58-4698-b5d3-8fd74e96f855.png alt={TEXT?}] 首先从天线的方向图上来看，达到了设计要求的，最大增益有9.59dBi，再中轴线上。 [upl-image-preview uuid=e5e7dd4e-d119-492b-9abb-23909bed29fc url=https://storage.hamcq.cn/2025-08-27/1756274025-30027-s11.png alt={TEXT?}] [upl-image-preview uuid=280350a1-506b-4c6d-a2a9-4ba8bdd4d618 url=https://storage.hamcq.cn/2025-08-27/1756274025-296555-vswr.png alt={TEXT?}] 再看端口，在144-146MHz范围内S11都在-20dB一下，驻波比在1.2以下。因此这个八木不需要考虑阻抗匹配的问题，直接接上就行。 [upl-image-preview uuid=60abb804-6785-448e-8042-0dfa033b4335 url=https://storage.hamcq.cn/2025-08-27/1756274065-715139-60abb804-6785-448e-8042-0dfa033b4335.png alt={TEXT?}] 最后附上尺寸图，使用4mm直径的铜管。欢迎大家交流指正！！

[upl-image-preview uuid=0fc234e8-2ea0-4ea9-ae61-4fd1c22f3d3e url=https://storage.hamcq.cn/2025-08-27/1756283102-819171-3cny.png alt={TEXT?}] [upl-image-preview uuid=5f3ebc64-5e48-4255-a2da-14c6e24fa3d5 url=https://storage.hamcq.cn/2025-08-27/1756283102-399864-3cny.png alt={TEXT?}] [upl-image-preview uuid=fdab757a-9afd-428e-a7ea-5e5f98a87247 url=https://storage.hamcq.cn/2025-08-27/1756283225-623352-fdab757a-9afd-428e-a7ea-5e5f98a87247.png alt={TEXT?}] 去掉后端的两个引向器，有源振子加长7mm后形成一个3单元八木，增益降到了7.4dBi，但带宽获得了比较大的提升。如果对于方向性要求没那么高的话，3单元貌似也够了。

振子的直径以及振子空心实心，对天线影响大吗

@"BA4SUA"#p76473 直径有影响，是否空心应该影响不大

@"BA4SUA"#p76473 仿真的结果上看，振子直径增大会使驻波比变大，从2mm变到6mm，驻波比变大0.02左右，可以忽略不计。其次，振子直径增大会使得天线的最大增益变大，从2mm变到6mm，增益变大0.12db，也可以忽略不计。振子实心和空心对天线性能和参数没有影响。总结一下，振子长度和间距两个参数会明显影响天线的性能，材质会比较明显的降低增益，粗细和空心的影响可以不考虑。

@"BG5FUM"#p76510 中心频率435，九单元，能不能帮我模拟一下比较优化的振子尺寸和间距

@"BA4SUA"#p76578 没问题啊，你把基本结构和尺寸发我吧，我微信号就是我的呼号

@"BG5FUM"#p76589 [upl-image-preview uuid=3d216613-fb47-45ec-a1aa-65fc375773f5 url=https://storage.hamcq.cn/2025-08-28/1756375708-698902-341881f7-b779-415e-9392-acfcb60dda8e.jpg alt={TEXT?}]

@"BA4SUA"#p76594 振子的材质和尺寸有了吗，还是按照理想状态进行仿真

@"BG5FUM"#p76601 材质是铁丝，晾衣架做的😀振子尺寸图中标了的，请帮我看看增益和驻波比，我没用天分测过。如果需要优化的，哪些尺寸该调整

@"BA4SUA"#p76602 OK，那我明天建个模型跑一下看看

I have simulated a 5-element Yagi antenna using CST, and the results look promising. I'd like to share it with everyone for discussion.

BG5FUM

BG7MGW

BG5FUM Based on this table, doesn't a value of 435 for "驻波" seem quite high?

BI1NIZ

Let's create a dedicated area for amateur radio electromagnetic simulation. I've been really enjoying using HFSS lately, it's so addictive!

Recently simulating OK1DFC septum feed.

BG5FUM

BI1NIZ Have you tried CST? I personally find it more intuitive and easier to use for modeling, compared to SeaFly.

BI1NIZ

BG7MGW The 420M metric is really good.🤣

BG7MGW

BI1NIZ This differs from my MMANA simulation and actual testing results. The actual test showed a resonant frequency of around 1.0 for the 435 mode, and 1.3 for both the 430 and 440 modes, which are similar to the curves generated by the MMANA simulation.

BG5FUM

BG7MGW Generally, when designing microwave devices, the minimum requirement is that the reflection within the bandwidth should be less than -20 dB. This translates to a standing wave ratio (SWR) of approximately 1.2. As you can see from the simulation results in my previous post, we have essentially achieved this within the specified bandwidth.

BG5FUM

BG7MGW The dimensions of the main beam and the method of connecting it to the resonator will all affect the resonant frequency, so adjustments are necessary. I believe that simulation is useful for guiding us to understand how each parameter affects the resonant frequency, resonant strength, and antenna directivity.

BG7MGW

BG5FUM Yes, simulation is based on reference data; real-world environments will always differ, and I want to see what the major differences are between different simulation software.

BA4ICQ

BI1NIZ This is how my gamma arm turned out.

BA4ICQ

Previously, I built one with a narrower bandwidth. When testing the diamond standing wave antenna at 10W power and a resonant frequency of 441 Hz, the measurements showed that the signal was below 1.1 in the range of 430-438 Hz and at 440 Hz. The main objectives for this project are threefold: firstly, to reduce the bandwidth of the original antenna; secondly, to add a reflector and shorten the main beam length to improve portability; and thirdly, to design it for easy assembly without tools.

I am preparing to adjust the lengths and spacing of each oscillator.

BA4ICQ

BI1NIZ How does the copper tube on the exterior wall achieve both sliding and fixing simultaneously? My current approach is to adjust the overall length of the gamma arm after installation to adjust the capacitance of the inserted cable.

BA4ICQ

Hi, could you please take some time to run a simulation using CST? I've already done one using MMA, and the results seem reasonable. Could you compare the two software packages to highlight any differences? Thanks.
The power supply mode and the previous one are both gamma-matched.

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